The present disclosure relates to a plasma processing apparatus, and more particularly, to a plasma processing apparatus for removing various impurities deposited on a substrate.
A semiconductor device and a flat panel display device are fabricated through a deposition process and an etching process. That is, a semiconductor device and a flat panel display device are fabricated by forming a thin layer on a predetermined region of a substrate through a deposition process and forming desired circuit patterns or circuit devices on the substrate by removing an unnecessary portion of the thin layer through an etching process using an etch mask.
However, since the thin layer is formed on the entire front surface of the substrate during the deposition process and then only a portion of the thin layer formed on a center region of the substrate is destined for an etch target during the etching process, a portion of the thin layer corresponding to an edge region of the substrate remains unremoved. Also, by-products of the process, for example, particles are inevitably deposited during the etching process. Also, generally, since the substrate is mounted on a substrate support using an electrostatic force or a vacuum force, the substrate and the substrate support are spaced apart from each other by a predetermined distance to generate a gap, and a thin layer and particles can be deposited on the rear surface of the substrate through this gap. When subsequent processes are performed without removing the particles and thin layers deposited on the substrate, the substrate may be deformed or the alignment of the substrate becomes difficult.
Therefore, a plasma processing apparatus for etching/removing the particles and thin layers deposited on the edge region of the substrate is under development recently. In such a plasma processing apparatus, a substrate is mounted on a substrate support having a smaller diameter than the substrate to expose the edge region of the substrate, and upper and lower electrodes are disposed in an upper and lower sides of the edge region of the substrate to generate plasma on the exposed edge region of the substrate. Penetration of plasma toward the center region of the substrate is prevented by decreasing a gap between the substrate support and a plasma blocking unit disposed on the upper region of the substrate.
However, according to the above-described conventional method, the substrate is seated on the substrate support having a smaller diameter than the substrate, and the exposed edge region of the substrate is etched using plasma to remove particles that are deposited on the edge part, i.e., edges of the top and rear surfaces of the substrate and the side surface of the substrate. Therefore, the particles deposited on the center of the rear surface of the substrate can't be completely removed using the conventional method. Further, according to the conventional method, there is not provided a separate substrate sensor for accurately controlling the gap between the upper electrode and the substrate support and the alignment of the substrate seated on the substrate support. Even if the substrate sensor is provided, light output from the substrate sensor is obstructed by the upper electrode. Thus, the conventional method frequently causes the misalignment of the substrate.